For high speed networks, particularly in the home, there is a need for a communication system which is efficient, which minimises the bandwidth required in the cables (and the corresponding radiation from the cables), and which minimises the cost and complexity of any repeaters, bridges, or routing switches in the network, and which places no constraint on the topology required of a network in order that the network functions.
A number of bridging, routing and switching technologies exist which have some, but not all, of the desirable properties required for a high speed network.
IEEE 1394 does not have a routing network, but is logically a bus with every node seeing every bit. Many of the packets are asynchronous packets which go from one source to one destination, and this is very wasteful of cable bandwidth. IEEE 1394 has bridges to isolate logical buses, but the bridges are not simple devices and are likely to be expensive.
ATM uses switches and makes efficient use of bandwidth. However, ATM is designed for a global network, and consequently has complications therein far beyond what is necessary for a high speed network in the home.
The STC104, used for IEEE 1355, is much simpler than ATM and this makes it possible to build the STC 104 with 32 full-duplex serial ports. The chip is, however, one of the largest chips made, and has around 28 k bits of memory--memory all made up of special registers. The STC 104 only provides for unicast packets, i.e. where message packets are transmitted from a single source to a single destination. Multicast packets where transmissions from a single source to multiple destinations or broadcast where transmission is from a single source to all destinations is desirable for a home network.
The ICR C416 is a simple routing switch, with physical routing which requires no initialisation. The ICR C416 uses one byte of header for each routing switch between source and destination, stripping the header at each switch. Like the STC 104, output ports can be grouped, so that several ports become logically a single port with higher bandwidth. Again, however, like the STC 104 it supports only unicast, (and not multicasting or broadcasting of packets).
Thus, it would be desirable to provide a routing switch suitable for a high speed network, particularly in the home, which was capable of routing packets or cells from a source to a single destination (i.e. unicast), to multiple destinations (i.e. multicast) and to all destinations (i.e. broadcast). In addition, for use in a home network, any routing switch must be compatible with any topology the untrained user arbitrarily constructs.
The routing switch must be capable, for use in a home network, of minimising bandwidth, power consumption, and RFI emissions, so that traffic should only travel on links necessary for the connection. In addition, it is essential that costs must be minimised, within the constraint of providing the necessary functionality and efficiency.